The Food and Drug Administration (FDA) regulates the manufacture of test kits for the detection of HIV-1, HIV-2 and HTLV-I infection. As part of the regulation of these tests the FDA requires every lot of kits to pass a lot release test. In this study we have analyzed HTLV-I lot release data to determine the lot-to-lot variability of the kits over time and to determine the characteristics of specimens that make up a "good" panel member. The kits monitored were from Abbott Labs, Cambridge Biotech, Cellular Products, and Organon Teknika. The lot release panel used was panel 2F which contained 8 required positive, 2 not required positive and 2 negative specimens. All kits submitted for lot release passed the release criteria. The sensitivity of kits varied in their ability to detect the "not required" panel members. The Organon kit routinely detected 10 of 10, Abbott 9 of 10, and Cambridge and Cellular Products 8 of 10. The Coefficient of Variation (C.V.) for the kit cutoff factor ranged from 6 to 28%, while the C.V.'s for individual panel members ranged from 11 to 43%. Trend analysis (linear regression) of all panel members found no significant changes in kit sensitivity (slope was not significantly different than zero) during the study period. These studies allow for the preparation of a new lot release panel based upon the lower limit of variation for each test. In addition, the defining of kit variation allows for more critical monitoring of changes in kit sensitivity. These analytical methods can be easily applied to lot release panels for HIV-1 and HIV-2 antibody detection tests to improve the monitoring of test kit consistency.